Looking At Buch: Strikezone Plots, Umpires, And Whining About Umpires Using Strikezone Plots

by Matt on April 21, 2011

in Red Sox

screenshot from mlb.tv

It’s not good form to whine about umpires.  There will be bad calls on both sides (though far more good than bad) and over a long season it will even out.  So despite the hilarious title of this post, what I’m about to write isn’t intended as umpire criticism.

With the preamble out of the way, the small portion of the season we’ve experienced so far has highlighted how the Red Sox will sink or swim on the strength of their starting pitching staff.  This is no great revelation.  Based on past performance we have a good idea this iteration of the Red Sox will hit and hit well.  Any mystery comes the starting rotation.  The cavalcade of questions: Is the Josh Beckett of the last two starts for real? Is Clay Buchholz really this bad? Are Daisuke Matsuzaka and John Lackey the nosy neighbor and the wisecracking butler characters in a new NBC sitcom starring John Wasdin?

For the record I hope the answers are yes, no, and if so kill me.  I bring this all up because last night’s effort by Clay Buchholz did not rate highly on the Promise-o-Meter (all meters must have O’s in their names; it’s required by the United American Meter Association of America).  In a performance straight from the Daisuke Matsuzaka School of Pitching Economy, Buchholz threw 102 pitches over 5.1 innings, striking out two while walking four.  The end result was effective if not encouraging (1 run allowed; special thanks to Daniel Bard).  However, I believe there to be some extenuating circumstances.  Namely, home plate umpire Mike DiMuro’s strikezone.  The below strikezone plot shows Clay Buchholz’s pitches last night:

By my count, Buchholz was the recipient of two strike calls outside the zone.  He was also on the receiving end of fourteen pitches that appear to be in the strikezone but which were called balls.  I should stress that the strikezone plot above is not perfect in that while the width of the plate is static, players are different heights and therefore the zone fluctuates vertically depending on the batter.  Still, that appears to be a remarkable number of pitches called balls which Pitch f/x says are strikes.

For the game, Buchholz threw 59 of his 102 pitches for strikes, a mediocre 57% strike rate.  If you give him half the the fourteen pitches mentioned above, that rate jumps to a more palatable 65% and my guess is the strikeouts make a small climb while the walks slightly shrink.

None of this is intended to say Buchholz pitched well or the home plate umpire is terrible or to make any other such statement.  The strikezone plot tells the story of an umpire not calling low strikes, which is something Buchholz should have realized and adjusted to after a certain point.  However, for a pitcher who lives down in the zone as much as Buchholz, not getting those calls, and not getting that many of them, certainly puts a crimp in his effectiveness.  Maybe Buchholz wasn’t quite as bad on Wednesday as the numbers suggest.

{ 5 comments… read them below or add one }

PossumAloysiusJenkins April 21, 2011 at 1:04 pm

Now this is some f’reals analysis! This is why I plan on renewing my subsription to RSB at the end of the year.

“Still, that appears to be a remarkable number of pitches called balls which Pitch f/x says are strikes.”
– I wish you had been able to give some perspective on what the norm is, and what is generally considered to be a remarkable number.


Matt April 21, 2011 at 1:20 pm

I wish I could too. It’s really a game by game type of thing. I’d say though, in my experience looking at this sort of data, 14 is a larger than usual number, which is why I chose to write about it. Sorry I can’t be more specific.


PossumAloysiusJenkins April 21, 2011 at 1:27 pm

Alright, I don’t know what resources you high-flying statdudes have at your disposal, so I thought maybe it was available.

Here’s to a happy new chapter being written tonight in Josh Beckett’s Magical 2011 Season!


BigNachos April 21, 2011 at 1:30 pm

According to pitch f/x analysis I’ve seen, umpires are about 80% accurate at calling strikes and 90% accurate at calling balls. So, 14 miscalled balls is pretty unusual, considering only a fraction of Buchholz’s 102 pitches are actually subject to an umpire’s call.


BigNachos April 21, 2011 at 1:36 pm

Er, that should be 95% accurate at calling balls, with an overall accuracy of about 90%.

There’s some selection bias in calling strikes, since pitches that are easy strike calls are often swung at (and vice versa for easy ball calls), so the strikes umpires have to call tend toward the borderline ones.


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